Thin film capacitor and electronic circuit board

Abstract

A thin film capacitor for which electrode conductivity is high and electrode irregularities are unlikely to be generate even if the capacitor if heated up to 700° C. This thin film capacitor has a first electrode, a dielectric layer, and a second electrode. The dielectric layer contains an ABO2N-type oxynitride. The nitrogen concentration of the part of the dielectric layer that contacts the first electrode is no more than half the nitrogen concentration of the center part of the dielectric layer.

What is claimed is: 
     
       1. A thin film capacitor comprising a first electrode, a dielectric layer, and a second electrode,
 wherein the first electrode includes Cu, 
 the dielectric layer includes an ABO 2 N type oxynitride, 
 a nitrogen concentration of the dielectric layer contacting the first electrode is half or less of a nitrogen concentration of a middle region of the dielectric layer, 
 the A element of the ABO 2 N type oxynitride is at least one selected from the group consisting of Sr, Ba, Ca, La, Nd, Na, and K, 
 the B element of the ABO 2 N type oxynitride is at least one selected from the group consisting of Ta, Nb, Ti, and W, 
 the dielectric layer includes a buffer layer contacting the first electrode, 
 the buffer layer contacting the first electrode includes an amorphous structure, 
 the buffer layer includes the A element of the ABO 2 N type oxynitride and the B element of the ABO 2 N type oxynitride, and 
 a total content of the A element represented by a1 included in the buffer layer and a total content of the B element represented by b1 included in the buffer layer satisfies 1.3≤a1/b1≤2.5. 
 
     
     
       2. The thin film capacitor according to  claim 1 , wherein the ABO 2 N type oxynitride represented by a compositional formula of A a B b O o N n  (a+b+o+n=5) satisfies n<1.0. 
     
     
       3. The thin film capacitor according to  claim 1 , wherein the total content of the A element represented by a1 included in the buffer layer and the total content of the B element represented by b1 included in the buffer layer satisfies 1.3≤a1/b1≤2.3. 
     
     
       4. The thin film capacitor according to  claim 1 , wherein the dielectric layer is in direct physical contact with Cu of the first electrode and part of Cu is oxidized. 
     
     
       5. An electronic circuit board comprising an epoxy based resin substrate, a resin layer formed on the epoxy based resin substrate, the thin film capacitor according to  claim 1  provided on the resin layer, an insulation coating layer formed on the resin layer, an electronic component provided on the insulation coating layer, and a metal wire connecting to the thin film capacitor or the electronic component.